these pleas coming from all the law enforcement agencies here. they keep on asking people, if you've seen anything unusual near you, around you, the last few days, please contact them immediately. susan candiotti, our thanks to you. >> you know, it's getting tricky here. because on one level you have virginia tech, columbine, oklahoma city, all in april. copycats, motivated? they don't know -- certainly not foreign terrorism. then, they start figuring out the bomb. everything shifts. why? 2010, faisal shahzad. you remember the times square bomber. he used it here. why? familiar, recognizable. allows them to trace ingredients and methods. now they're back. now they're accelerating. let's bring in tom fuentes. a cnn analyst, he helps us all the time with this type of stuff. he's also a former assistant director with the fbi. great to have you mr. fuentes. let's bullet point this. people at home, they hear about this, oh, it seems exotic. oh, this is going to be hard. maybe it's a one-off. actually the opposite is true, right? >> good morning, chris